Institute for Cyber Security. Authorization and Trust in the Cloud

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1 Institute for Cyber Security Authorization and Trust in the Cloud Prof. Ravi Sandhu Executive Director and Endowed Chair USECSW May 29, 2013 Joint work with Bo Tang and Qi Li World-Leading Research with Real-World Impact! 1

2 Cloud Computing Shared infrastructure [$$$] -----> [$ $ $] Multi-Tenancy Virtually dedicated resources Drawbacks: Data Locked-in o Collaborations can only be achieved through desktop. o E.g.: open files in Box with GoogleDoc. How to collaborate? Source: World-Leading Research with Real-World Impact! 2

3 Collaborative Access Control Centralized Facility Chance for centralized models in distributed systems Agility Collaboration and collaborators are temporary Homogeneity Handful of popular brands Out-Sourcing Trust Built-in collaboration spirit World-Leading Research with Real-World Impact! 3

4 Market Place Microsoft and IBM: Fine-grained data sharing in SaaS using DB schema Only feasible in DB NASA: RBAC + OpenStack Lacks ability to support collaborations Salesforce (Force.com): SSO + SAML Focus on authentication Heavy management of certificates Source: World-Leading Research with Real-World Impact! 4

5 Literature RBAC CBAC, GB-RBAC, ROBAC Require central authority managing collaborations Delegation Models drbac and PBDM Lacks agility (which the cloud requires) Grids CAS, VOMS, PERMIS Problem: semantic mismatch Absence of centralized facility and homogeneous architecture (which the cloud has) World-Leading Research with Real-World Impact! 5

6 Literature (Contd.) Role-based Trust RT, Traust, RMTN AND RAMARS_TM Calero et al: towards a multi-tenant authorization system for cloud services o Implementation layer PoC o Open for extensions in trust models Suits the cloud (out-sourcing trust) Challenge: trust relation World-Leading Research with Real-World Impact! 6

7 Multi-Tenant Authorization as a Service (MT-AaaS) MT-AaaS Multi-Tenant Access Control Cross-Tenant Access World-Leading Research with Real-World Impact! 7

8 MTAS Trust Model If A trusts B then B (resource owner) can assign B s permissions to A s roles; and B s roles as junior roles to A s roles. Tenant A Tenant B If No trust Resources AuthStmts Resources AuthStmts If A trust B Resources AuthStmts Resources AuthStmts User World-Leading Research with Real-World Impact! 8

9 MTAS World-Leading Research with Real-World Impact! 9

10 MT-RBAC Trust Model If B (resource owner) trusts A then A can assign B s permissions to A s roles; and B s roles as junior roles to A s roles. Tenant A Tenant B If No trust Resources AuthStmts Resources AuthStmts If B trust A Resources AuthStmts Resources AuthStmts User World-Leading Research with Real-World Impact! 10

11 MT-RBAC World-Leading Research with Real-World Impact! 11

12 Trust Model Comparison A: resource owner B: resource requester World-Leading Research with Real-World Impact! 12

13 Finer-grained Trust Models World-Leading Research with Real-World Impact! 13

14 Constraints Role Cycles: lead to implicit role upgrades in the role hierarchy. SoD: conflict of duties Tenant-level o E.g.: SOX compliance companies may not hire same the same company for both consulting and auditing. Role-level o Across tenants Chinese Wall: conflict of interests among tenants. World-Leading Research with Real-World Impact! 14

15 Collaboration Admin. Decentralized management Trusters maintain the trust relation Immediately effective when trust changes Automatic revocation of cross-tenant accesses Agility in cloud environments World-Leading Research with Real-World Impact! 15

16 PROTOTYPE AND EVALUATION Cloud Service CloudStorage: an open source web based cloud storage and sharing system. Authorization Service Centralized PDP Distributed PEP World-Leading Research with Real-World Impact! 16

17 Evaluation: Performance MT-RBAC vs RBAC More policy references incur more decision time MT-RBAC 2 introduces 6.82% overhead in average. Performance comparison at PDP File retrieval delay ratio introduced World-Leading Research with Real-World Impact! 17

18 Evaluation: Scalability Scalable by either Enhancing PDP capability; or Increasing PEP amount. Different Flavors of PDP Different Numbers of PEP World-Leading Research with Real-World Impact! 18

19 Summary Collaboration needs in the cloud eco-system Novel service model: MT-AaaS Proposed formal models MTAS MT-RBAC Constraints and administration Prototype and evaluation Performance overhead 6.82% Scalable in the cloud Trust Model Comparison World-Leading Research with Real-World Impact! 19

20 Future Work OpenStack Keystone extensions Integrate trust into ABAC: MT-ABAC Unified trust framework for the cloud World-Leading Research with Real-World Impact! 20

21 Institute for Cyber Security Q & A Bo Tang, Ravi Sandhu and Qi Li. Multi-Tenancy Authorization Models for Collaborative Cloud Services. CTS, Bo Tang, Qi Li and Ravi Sandhu. A Multi-Tenant RBAC Model for Collaborative Cloud Services. PST World-Leading Research with Real-World Impact! 21